The Professor reviews the RFA200 external ferrite antenna

Many thanks to SWLing Post contributor, The Professor, who shares the following review of the RFA200 external ferrite antenna:

The Tecsun R-9012 and RFA200 MW antenna (Photo credit: The Professor)

A Quick Review of the RFA200

The Professor

I’ve considered saying something here about RFA200, as I bought one of these not long after its existence was announced on this blog a few months ago, but I’ve been hesitating because I didn’t have much good to say about it. A couple of times I’ve placed it up snug up against the the top of the two Tecsun sets I have handy (the PL-310ET and the PL-880) and found that despite a lot of knob turning it had little or no effect on improving signal on medium wave stations. I was not impressed.

But I guess I’ve kind of changed my mind on that. And oh yeah, I bought another radio. It’s funny how you can talk yourself into things when you’re talking someone else into something. But after I had mentioned to a reader here the other day that the very inexpensive Tecsun R-9012 was a worthy analog DX portable, I decided to drop twenty and pick one up for myself. After all, it was about the same price as a fancy Brooklyn hamburger. It arrived a couple days ago.

So, I have been playing with it a bit over the last few days. It’s as good as the other ones I’ve had which are the same basic radio (I’d mentioned that the bandswitch slider broke in a couple of mine). It’s single conversion. The bandwidth is a little wide, but it’s a very sensitive and simple analog set.

Yesterday I was going through the AM band and remembered that ferrite from Greece, and I pulled it out recalling that in my experience some radios are more susceptible to reception improvements using passive loops than others. Maybe this ferrite bar might be similar. And sure enough, the antenna made a notable difference this time. By placing it up against the R-9012 and tuning the thing I could certainly increase signal a bit. And I could even see it in the slight brightening or steadiness of the tuning light.

So, not a total waste money after all. I would emphasize that the difference in reception doesn’t seem to be as dramatic or sustaining as you might hear with a tunable loop antenna next to your radio. But it’s not junk either. Then again, for fifty dollars shipped it is a little pricey. Twice as much as a Tecsun tunable loop antenna, and two and half times more expensive than the R-9012 itself.

I found the best way to use this antenna is to tune the radio separately first and when you find a weaker signal you want to improve physically go ahead and rotate the radio until the signal is strongest and THEN put the antenna along the top of the radio and adjust the tuning knob on the antenna. Focus in on strengthening the signal you actually hear, going back and forth until it gets strongest. If you seem to be pulling up other stations it’s because the antenna adjustment will bring in adjacent stronger stations if you move it too far either way.

I’m surely not able to pin down the science involved in exactly how these things work, but perhaps somebody can chime in on this. I’m wondering if analog radio tuning in particular is better suited to the use of these tunable passive antennas, as opposed to PLL and DSP radios?

If you buy one of these be prepared to wait. At least mine took weeks to get here from Greece. And don’t expect miracles. But it seems rather well constructed, and will probably work with some radios. The seller has a 100% rating on eBay and has all sorts of interesting antennas for sale. I’m glad to see people succeeding in that business.

Many thanks, Prof, for sharing your fine review of the RFA200! Thanks for also mentioning the Tecsun R9012–I purchased one a couple years ago with the intention of reviewing it, then gave it to teenager who expressed interest in shortwave. I don’t think I actually put it on the air myself. I do enjoy simple old school analog radio–especially when making band scans.

Last days I received an RFA200 (MW) and also an RFL200 (LW).
I made a short test without direct connection with a Tecsun PL-600 unit on MW and LW.
I can say that both antenna worked well 🙂
In a few days I’ll upload a video to show how the two booster works.

I have the Q stick, the TERK and the SAT commercially made loops, as well as 4 PK models. I just ordered this RFA200 hoping to use the 50 Ohm input to couple my outdoor antennas which have baluns and co-ax lines. I like the Qstick for a compact portable antenna. It does not boost signals as well as the TERK and SAT, which is alluded to in the mfg. description. If the RFA200 jack does not connect to couple an outdoor antenna to a portable without AM terminals, I will try a 3-5 turn winding over the PVC. In the photo at the top of the page, the RFA200 ferrite is some distance from the ferrite in the radio. Try it upside down on top of the radio so the two ferrites are as close as possible. And yes, these small loops don’t help the best AM portables. Results vary with lesser radios. The much larger tuned PK loops are much better.-FARMERIK

Digression: Guy, the price of lots of materials has gone insane! I suppose it depends on what exactly is in that ferrite formula: any rare earths would certainly jack it up. Also, lots of things that before were, for lack of a better term, “non-military” now are classified “dual use” and covered by “reporting requirements” and the like, so the prices have gone up or, in some cases, the items can no longer be sold in the open market. I wish I had links to this info but I’m typing this from work with a headache. 90% of this happened in the last decade or less when they finally started getting really scared of (mainly) China and Russia.

On passive ferrite loops (and air-core loops): they are basically weakly-coupled extra antennas doubling as pre-selectors. Since we’re talking ferrite cores in this case, its a fancy magnetic antenna and a bigger core (especially with more Mu / Permeability) increases your effective capture area, a big deal with big wavelengths.

My guess why they perform better with some radios rather than others: shielding of the antenna(s) in the radio(s), in the antenna assembly (metal or plastic box, especially around the cap?), and how much energy gets in at those frequencies through the radio’s whip (which, in theory, could cause some cancellation depending on delays through the 2 antennas).

Obviously a direct connection nips this in the bud, assuming the internal antenna can be disconnected (you may have to mod it).

Oh, one last thing: on that Stormwise antenna (which I’ve been eyeing and why I’m here in this post thanks to Google), the “optional” capacitor is only optional if you already have one to resonate it: otherwise you just have a very big inductance. Other than AM broadcast, you usually want to make your bandwidth as narrow as the signal will allow, which means high Q values: fortunately, Litz wire works well in this range (and I’m assuming that’s what these companies are using, but I have yet to ask).

Professor, Does the antenna jack turn off the loop-stick inside the radio? Most portables shut off the whip from the radios in the shortwave mode but not on the broadcast and long wave mode. A quick way to test would be to plug in a shorting plug into the antenna jack and listen. I have only one radio, Heath GR78 that works well with external antennas because it does not have an internal loop stick.

I have one of these Greek rods as well and have just returned from a trip collecting spectrum using it. I have found it to be totally wonderful BUT I have not been using it in its coupling mode, I have been using the direct connection (the rod also has a wired antenna port) with an AirSpy HF+ SDR. The results are amazing. For a long time, I have been looking for a very compact travel MW antenna for use with my WinRadio Excalibur, KiwiSDR and AirSpy HF+. The RFA200 fits the bill perfectly for me, I have found it to be fantastic, performing surprising well! The build quality is good, it’s super small (much smaller than I was expecting) – it’s totally travel-friendly!

I was doing some more experimenting with this antenna this evening, and have a couple of things to add about it. For one, I powered up my current pride and joy the GE 7-2990 (a large early 80s portable similar to the Panasonic RF-2900) and found no reception benefit from using this passive antenna. Perhaps it has more of an affinity to radios that have smaller ferrite antennas inside, although it didn’t seem to do much for my Tecsun PL-310ET.

However, I remember reading that ultralight radio expert Gary DeBock mentioned that these small Chinese analog sets offer better sensitivity if you pull the antenna up from it’s horizontal resting positing and aim it vertically (but unextended). I found that doing this with my Tecsun R-9012 actually gave this tunable external ferrite more sway over reception as well. It didn’t necessarily pull weak stations out of the noise floor, but it often provided fuller audio reception for somewhat struggling signals, specifically a little more “bottom” to the sound as I was listening with headphones.

Again just to mention that I haven’t tuned one of these small Chinese analog portables for a while, but the Tecsun R-9012 is really something on AM. And having a tuning knob rather than a thumb wheel as some do is a real advantage for DXing. From here in Brooklyn WSB in Atlanta was quite strong at 750kHz and it pulled out WJR at 760kHz from under the shadow of powerhouse WABC nextdoor at 770kHz. And I also got a pretty good read on a small Rochester, NY station I’m not sure I’ve heard before, WCJW at 1140kHz.

While it doesn’t have the light up dial, fuller audio or most of the other the bells and whistles of the new CC Radio EP Pro, I think it’s safe to say the Tecsun R-9012 is probably a better set for the seasoned MW DXer, and especially at less than a quarter of the price of the fancier analog tuned DSP radio. I’d love to see somebody do a head to head comparison between the two on medium wave.

Tom Servo (aka Zach) and I discovered that when a Q-Stick is used with
a PK LW Loop the coupling effect is greatly enhanced…the standard 14
inch loop performs much like the 20 inch.
It was named the Rutledge Effect in his honor.?

Prof,your findings were similar to mine.These things work by
interacting with the receiver’s ferrite bar antenna by inductive
coupling (also called loose coupling since there is no direct
contact).
At $51 bucks delivered it’s pricey…you could do much better
for less money with a Tecsun AN-100 or AN-200 loop (but
only Anna at Anon Co. has them now).
For about 20 bucks more you can go with the Q-Stick:

They have products going from VLF to shortwave (up to 4 MHZ) in different physical sizes; a distinguishing feature is that the tuning capacitor is optional, and mounted external to the device across its terminals.

Stormwise used to sell plastic-encapsulated ferrite rods for long wave / medium wave use that were as long as 18 inches, for the same cost as their 12 inch model is priced now. I used one of the 18″ X 1.0″ diameter rods years ago to make a booster antenna. This was well before the Ferrite Sleeve Loop (FSL) antennas I experiment with now.

Correction! I’m not sure what I was first looking at on the Stormwise site, but I now see they do still carry the 1″ X 18″ ferrite rods, as well as and even bigger 1″ X 22.5″ rod. Yikes! – Pricing is $192 and $240 respectively!

When I purchased the 1″ X 18″ rod some years ago, the cost was $40… a more reasonable cost for high performance MW antenna experimentation.

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